Mass storage non-volatile memory (NVM) devices enable read and/or write access to data containing many bytes. Mass storage devices are typically, but not only, used in applications such as hard disks, or digital video storage devices, such as for digital cameras. Throughout the specification and claims, the term “mass storage device” refers not only to memory devices that are capable of the storage functionality of hard disks or video storage devices and the like, but also to memory devices capable of storing and providing access to at least 512 megabyte (MB) of data or to memory devices requiring very fast programming and read access rates. The amount of data accessible with the mass storage device may include “blocks” of data. A “block” is defined as a basic amount of data containing a certain amount of bytes. For example, a block may contain 256 bytes (256B), 512B, 528B or any other number of bytes.
In mass storage NVM devices, read and program operations may be performed in a block granularity, i.e., on a single block. Erase operations may be performed on a single block or groups of blocks. Such groups of blocks are defined as “erase sectors” (E-sectors). For example, an E-sector may contain 8 blocks, 32 blocks or 64 blocks or any other number of blocks.
Mass storage NVM devices generally require extremely fast programming rates and fast burst read access. As a relative example, mass storage devices require programming rates at least 2–10 times faster than currently standard code flash devices. In read operations, first byte latency of a few microseconds may be acceptable, but fast burst read capability in the range of tens of nanoseconds is generally required.
In addition to the program, erase and read requirements mentioned above, mass storage NVM devices may require a very dense array architecture due to the large amount of data stored in a single chip. In currently standard floating gate technology, both NAND and NOR array architectures are used for mass storage applications. The NAND architecture is generally denser than NOR, while NOR is generally more reliable and robust than NAND.